1
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Bladwell S. Spin Polarization via Adiabatic and Counterdiabatic Engineering. PHYSICAL REVIEW LETTERS 2024; 133:047001. [PMID: 39121431 DOI: 10.1103/physrevlett.133.047001] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/31/2023] [Accepted: 06/20/2024] [Indexed: 08/11/2024]
Abstract
A spin filter is a device that allows only a single spin state to pass, equivalent to a polarizing filter for a beam of light. Here, taking inspiration from shortcuts to adiabaticity, I demonstrate that the potential landscape of a typical quantum point contact can be tuned to act as a two terminal spin filter or to generate a spin-polarized beam. The effect presented is sufficiently robust that rough engineering yields a significant effect, as demonstrated by experiments on asymmetrically biased quantum point contacts in InAs quantum wells.
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2
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Klanurak I, Watanabe K, Taniguchi T, Chatraphorn S, Taychatanapat T. Probing the Anisotropic Fermi Surface in Tetralayer Graphene via Transverse Magnetic Focusing. NANO LETTERS 2024; 24:6330-6336. [PMID: 38723237 PMCID: PMC11140744 DOI: 10.1021/acs.nanolett.4c01133] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/06/2024] [Revised: 05/04/2024] [Accepted: 05/08/2024] [Indexed: 05/15/2024]
Abstract
Bernal-stacked tetralayer graphene (4LG) exhibits intriguing low-energy properties, featuring two massive sub-bands and showcasing diverse features of topologically distinct, anisotropic Fermi surfaces, including Lifshitz transitions and trigonal warping. Here, we study the influence of the band structure on electron dynamics within 4LG using transverse magnetic focusing. Our analysis reveals two distinct focusing peaks corresponding to the two sub-bands. Furthermore, we uncover a pronounced dependence of the focusing spectra on crystal orientations, indicative of an anisotropic Fermi surface. Utilizing the semiclassical model, we attribute this orientation-dependent behavior to the trigonal warping of the band structure. This phenomenon leads to variations in electron trajectories based on crystal orientation. Our findings not only enhance our understanding of the dynamics of electrons in 4LG but also offer a promising method for probing anisotropic Fermi surfaces in other materials.
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Affiliation(s)
- Illias Klanurak
- Department
of Physics, Faculty of Science, Chulalongkorn
University, Patumwan, Bangkok 10330, Thailand
| | - Kenji Watanabe
- Research
Center for Electronic and Optical Materials, National Institute for Materials Science, 1-1 Namiki, Tsukuba 305-0044, Japan
| | - Takashi Taniguchi
- Research
Center for Materials Nanoarchitectonics, National Institute for Materials Science, 1-1 Namiki, Tsukuba 305-0044, Japan
| | - Sojiphong Chatraphorn
- Department
of Physics, Faculty of Science, Chulalongkorn
University, Patumwan, Bangkok 10330, Thailand
| | - Thiti Taychatanapat
- Department
of Physics, Faculty of Science, Chulalongkorn
University, Patumwan, Bangkok 10330, Thailand
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3
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Rao Q, Kang WH, Xue H, Ye Z, Feng X, Watanabe K, Taniguchi T, Wang N, Liu MH, Ki DK. Ballistic transport spectroscopy of spin-orbit-coupled bands in monolayer graphene on WSe 2. Nat Commun 2023; 14:6124. [PMID: 37777513 PMCID: PMC10542375 DOI: 10.1038/s41467-023-41826-1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2023] [Accepted: 09/20/2023] [Indexed: 10/02/2023] Open
Abstract
Van der Waals interactions with transition metal dichalcogenides were shown to induce strong spin-orbit coupling (SOC) in graphene, offering great promises to combine large experimental flexibility of graphene with unique tuning capabilities of the SOC. Here, we probe SOC-driven band splitting and electron dynamics in graphene on WSe2 by measuring ballistic transverse magnetic focusing. We found a clear splitting in the first focusing peak whose evolution in charge density and magnetic field is well reproduced by calculations using the SOC strength of ~ 13 meV, and no splitting in the second peak that indicates stronger Rashba SOC. Possible suppression of electron-electron scatterings was found in temperature dependence measurement. Further, we found that Shubnikov-de Haas oscillations exhibit a weaker band splitting, suggesting that it probes different electron dynamics, calling for a new theory. Our study demonstrates an interesting possibility to exploit ballistic electron motion pronounced in graphene for emerging spin-orbitronics.
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Affiliation(s)
- Qing Rao
- Department of Physics and HK Institute of Quantum Science & Technology, The University of Hong Kong, Pokfulam Road, Hong Kong, China
| | - Wun-Hao Kang
- Department of Physics and Center for Quantum Frontiers of Research and Technology (QFort), National Cheng Kung University, Tainan, 70101, Taiwan
| | - Hongxia Xue
- Department of Physics and HK Institute of Quantum Science & Technology, The University of Hong Kong, Pokfulam Road, Hong Kong, China
| | - Ziqing Ye
- Department of Physics and Center for Quantum Materials, The Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, 999077, Hong Kong, China
| | - Xuemeng Feng
- Department of Physics and Center for Quantum Materials, The Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, 999077, Hong Kong, China
| | - Kenji Watanabe
- Research Center for Electronic and Optical Materials, National Institute for Materials Science, 1-1 Namiki, Tsukuba, 305-0044, Japan
| | - Takashi Taniguchi
- Research Center for Materials Nanoarchitectonics, National Institute for Materials Science, 1-1 Namiki, Tsukuba, 305-0044, Japan
| | - Ning Wang
- Department of Physics and Center for Quantum Materials, The Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, 999077, Hong Kong, China
| | - Ming-Hao Liu
- Department of Physics and Center for Quantum Frontiers of Research and Technology (QFort), National Cheng Kung University, Tainan, 70101, Taiwan.
| | - Dong-Keun Ki
- Department of Physics and HK Institute of Quantum Science & Technology, The University of Hong Kong, Pokfulam Road, Hong Kong, China.
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4
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Lee YK, Smith JS, Cole JH. Influence of Device Geometry and Imperfections on the Interpretation of Transverse Magnetic Focusing Experiments. NANOSCALE RESEARCH LETTERS 2022; 17:31. [PMID: 35247127 PMCID: PMC8898212 DOI: 10.1186/s11671-022-03671-x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 11/04/2021] [Accepted: 02/19/2022] [Indexed: 06/14/2023]
Abstract
Spatially separating electrons of different spins and efficiently generating spin currents are crucial steps towards building practical spintronics devices. Transverse magnetic focusing is a potential technique to accomplish both those tasks. In a material where there is significant Rashba spin-orbit interaction, electrons of different spins will traverse different paths in the presence of an external magnetic field. Experiments have demonstrated the viability of this technique by measuring conductance spectra that indicate the separation of spin-up and spin-down electrons. However the effect that the geometry of the leads has on these measurements is not well understood. By simulating an InGaAs-based transverse magnetic focusing device, we show that the resolution of features in the conductance spectra is affected by the shape, separation and width of the leads. Furthermore, the number of subbands occupied by the electrons in the leads affects the ratio between the amplitudes of the spin-split peaks in the spectra. We simulated devices with random onsite potentials and observed that transverse magnetic focusing devices are sensitive to disorder. Ultimately we show that careful choice and characterisation of device geometry are crucial for correctly interpreting the results of transverse magnetic focusing experiments.
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Affiliation(s)
- Yik Kheng Lee
- Theoretical, Computational, and Quantum Physics, School of Science, RMIT University, Melbourne, Australia
- ARC Centre of Excellence in Future Low-Energy Electronics Technologies, RMIT University, Melbourne, Australia
| | - Jackson S. Smith
- Theoretical, Computational, and Quantum Physics, School of Science, RMIT University, Melbourne, Australia
- ARC Centre of Excellence in Future Low-Energy Electronics Technologies, RMIT University, Melbourne, Australia
| | - Jared H. Cole
- Theoretical, Computational, and Quantum Physics, School of Science, RMIT University, Melbourne, Australia
- ARC Centre of Excellence in Future Low-Energy Electronics Technologies, RMIT University, Melbourne, Australia
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5
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Smith LW, Chen HB, Chang CW, Wu CW, Lo ST, Chao SH, Farrer I, Beere HE, Griffiths JP, Jones GAC, Ritchie DA, Chen YN, Chen TM. Electrically Controllable Kondo Correlation in Spin-Orbit-Coupled Quantum Point Contacts. PHYSICAL REVIEW LETTERS 2022; 128:027701. [PMID: 35089765 DOI: 10.1103/physrevlett.128.027701] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/15/2021] [Accepted: 12/02/2021] [Indexed: 06/14/2023]
Abstract
Integrating the Kondo correlation and spin-orbit interactions, each of which have individually offered unprecedented means to manipulate electron spins, in a controllable way can open up new possibilities for spintronics. We demonstrate electrical control of the Kondo correlation by coupling the bound spin to leads with tunable Rashba spin-orbit interactions, realized in semiconductor quantum point contacts. We observe a transition from single to double peak zero-bias anomalies in nonequilibrium transport-the manifestation of the Kondo effect-indicating a controlled Kondo spin reversal using only spin-orbit interactions. Universal scaling of the Kondo conductance is demonstrated, implying that the spin-orbit interactions could enhance the Kondo temperature. A theoretical model based on quantum master equations is also developed to calculate the nonequilibrium quantum transport.
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Affiliation(s)
- Luke W Smith
- Department of Physics, National Cheng Kung University, Tainan 701, Taiwan
| | - Hong-Bin Chen
- Department of Physics, National Cheng Kung University, Tainan 701, Taiwan
- Department of Engineering Science, National Cheng Kung University, Tainan 701, Taiwan
- Center for Quantum Frontiers of Research and Technology (QFort), National Cheng Kung University, Tainan 701, Taiwan
| | - Che-Wei Chang
- Department of Physics, National Cheng Kung University, Tainan 701, Taiwan
| | - Chien-Wei Wu
- Department of Physics, National Cheng Kung University, Tainan 701, Taiwan
| | - Shun-Tsung Lo
- Department of Physics, National Cheng Kung University, Tainan 701, Taiwan
- Department of Electrophysics, National Yang Ming Chiao Tung University, Hsinchu 300, Taiwan
| | - Shih-Hsiang Chao
- Department of Physics, National Cheng Kung University, Tainan 701, Taiwan
| | - I Farrer
- Cavendish Laboratory, University of Cambridge, Cambridge CB3 0HE, United Kingdom
- Department of Electronic and Electrical Engineering, University of Sheffield, Sheffield S1 3JD, United Kingdom
| | - H E Beere
- Cavendish Laboratory, University of Cambridge, Cambridge CB3 0HE, United Kingdom
| | - J P Griffiths
- Cavendish Laboratory, University of Cambridge, Cambridge CB3 0HE, United Kingdom
| | - G A C Jones
- Cavendish Laboratory, University of Cambridge, Cambridge CB3 0HE, United Kingdom
| | - D A Ritchie
- Cavendish Laboratory, University of Cambridge, Cambridge CB3 0HE, United Kingdom
| | - Yueh-Nan Chen
- Department of Physics, National Cheng Kung University, Tainan 701, Taiwan
- Center for Quantum Frontiers of Research and Technology (QFort), National Cheng Kung University, Tainan 701, Taiwan
| | - Tse-Ming Chen
- Department of Physics, National Cheng Kung University, Tainan 701, Taiwan
- Center for Quantum Frontiers of Research and Technology (QFort), National Cheng Kung University, Tainan 701, Taiwan
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6
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Freudenfeld J, Geier M, Umansky V, Brouwer PW, Ludwig S. Coherent Electron Optics with Ballistically Coupled Quantum Point Contacts. PHYSICAL REVIEW LETTERS 2020; 125:107701. [PMID: 32955297 DOI: 10.1103/physrevlett.125.107701] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/28/2020] [Accepted: 08/07/2020] [Indexed: 06/11/2023]
Abstract
The realization of integrated quantum circuits requires precise on-chip control of charge carriers. Aiming at the coherent coupling of distant nanostructures at zero magnetic field, here we study the ballistic electron transport through two quantum point contacts (QPCs) in series in a three terminal configuration. We enhance the coupling between the QPCs by electrostatic focusing using a field effect lens. To study the emission and collection properties of QPCs in detail we combine the electrostatic focusing with magnetic deflection. Comparing our measurements with quantum mechanical and classical calculations we discuss generic features of the quantum circuit and demonstrate how the coherent and ballistic dynamics depend on the details of the QPC confinement potentials.
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Affiliation(s)
- J Freudenfeld
- Paul-Drude-Institut für Festkörperelektronik, Leibniz-Institut im Forschungsverbund Berlin e.V., Hausvogteiplatz 5-7, 10117 Berlin, Germany
| | - M Geier
- Dahlem Center for Complex Quantum Systems and Physics Department, Freie Universität Berlin, Arnimallee 14, 14195 Berlin, Germany
| | - V Umansky
- Weizmann Institute of Science, Rehovot 76100, Israel
| | - P W Brouwer
- Dahlem Center for Complex Quantum Systems and Physics Department, Freie Universität Berlin, Arnimallee 14, 14195 Berlin, Germany
| | - S Ludwig
- Paul-Drude-Institut für Festkörperelektronik, Leibniz-Institut im Forschungsverbund Berlin e.V., Hausvogteiplatz 5-7, 10117 Berlin, Germany
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7
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Lin BC, Wang S, Wang AQ, Li Y, Li RR, Xia K, Yu D, Liao ZM. Electric Control of Fermi Arc Spin Transport in Individual Topological Semimetal Nanowires. PHYSICAL REVIEW LETTERS 2020; 124:116802. [PMID: 32242698 DOI: 10.1103/physrevlett.124.116802] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/29/2019] [Revised: 11/25/2019] [Accepted: 01/28/2020] [Indexed: 06/11/2023]
Abstract
The exotic topological surface states of Dirac or Weyl semimetals, namely Fermi arcs, are predicted to be spin polarized, while their spin polarization nature is still not revealed by transport measurements. Here, we report the spin-polarized transport in a Dirac semimetal Cd_{3}As_{2} nanowire employing the ferromagnetic electrodes for spin detection. The spin-up and spin-down states can be changed by reversing the current polarity, showing the spin-momentum locking property. Moreover, the nonlocal measurements show a high fidelity of the spin signals, indicating the topological protection nature of the spin transport. As tuning the Fermi level away from the Dirac point by gate voltages, the spin signals gradually decrease and finally are turned off, which is consistent with the fact that the Fermi arc surface state has the maximum ratio near the Dirac point and disappears above the Lifshitz transition point. Our results should be valuable for revealing the transport properties of the spin-polarized Fermi arc surface states in topological semimetals.
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Affiliation(s)
- Ben-Chuan Lin
- State Key Laboratory for Mesoscopic Physics and Frontiers Science Center for Nano-optoelectronics, School of Physics, Peking University, Beijing 100871, China
- Institute for Quantum Science and Engineering and Department of Physics, South University of Science and Technology of China, Shenzhen 518055, China
| | - Shuo Wang
- State Key Laboratory for Mesoscopic Physics and Frontiers Science Center for Nano-optoelectronics, School of Physics, Peking University, Beijing 100871, China
- Institute for Quantum Science and Engineering and Department of Physics, South University of Science and Technology of China, Shenzhen 518055, China
| | - An-Qi Wang
- State Key Laboratory for Mesoscopic Physics and Frontiers Science Center for Nano-optoelectronics, School of Physics, Peking University, Beijing 100871, China
| | - Ying Li
- State Key Laboratory for Mesoscopic Physics and Frontiers Science Center for Nano-optoelectronics, School of Physics, Peking University, Beijing 100871, China
| | - Rong-Rong Li
- State Key Laboratory for Mesoscopic Physics and Frontiers Science Center for Nano-optoelectronics, School of Physics, Peking University, Beijing 100871, China
| | - Ke Xia
- Institute for Quantum Science and Engineering and Department of Physics, South University of Science and Technology of China, Shenzhen 518055, China
| | - Dapeng Yu
- Institute for Quantum Science and Engineering and Department of Physics, South University of Science and Technology of China, Shenzhen 518055, China
| | - Zhi-Min Liao
- State Key Laboratory for Mesoscopic Physics and Frontiers Science Center for Nano-optoelectronics, School of Physics, Peking University, Beijing 100871, China
- Collaborative Innovation Center of Quantum Matter, Peking University, Beijing 100871, China
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8
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Super-geometric electron focusing on the hexagonal Fermi surface of PdCoO 2. Nat Commun 2019; 10:5081. [PMID: 31705049 PMCID: PMC6841680 DOI: 10.1038/s41467-019-13020-9] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/12/2019] [Accepted: 10/11/2019] [Indexed: 11/08/2022] Open
Abstract
Geometric electron optics may be implemented in solids when electron transport is ballistic on the length scale of a device. Currently, this is realized mainly in 2D materials characterized by circular Fermi surfaces. Here we demonstrate that the nearly perfectly hexagonal Fermi surface of PdCoO2 gives rise to highly directional ballistic transport. We probe this directional ballistic regime in a single crystal of PdCoO2 by use of focused ion beam (FIB) micro-machining, defining crystalline ballistic circuits with features as small as 250 nm. The peculiar hexagonal Fermi surface naturally leads to enhanced electron self-focusing effects in a magnetic field compared to circular Fermi surfaces. This super-geometric focusing can be quantitatively predicted for arbitrary device geometry, based on the hexagonal cyclotron orbits appearing in this material. These results suggest a novel class of ballistic electronic devices exploiting the unique transport characteristics of strongly faceted Fermi surfaces. Ballistic electron beams in clean metals can be focused by passing currents through well designed contraptions, which is mostly done in isotropic materials described by a circular Fermi surface. Here, the authors demonstrate that the almost hexagonal Fermi surface of PdCoO2 gives rise to highly directional ballistic transport with enhanced electron self-focusing effects.
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9
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Width dependence of the 0.5 × (2e 2/h) conductance plateau in InAs quantum point contacts in presence of lateral spin-orbit coupling. Sci Rep 2019; 9:12172. [PMID: 31434942 PMCID: PMC6704071 DOI: 10.1038/s41598-019-48380-1] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/05/2019] [Accepted: 07/30/2019] [Indexed: 11/22/2022] Open
Abstract
The evolution of the 0.5Go (Go = 2e2/h) conductance plateau and the accompanying hysteresis loop in a series of asymmetrically biased InAs based quantum point contacts (QPCs) in the presence of lateral spin-orbit coupling (LSOC) is studied using a number of QPCs with varying lithographic channel width but fixed channel length. It is found that the size of the hysteresis loops is larger for QPCs of smaller aspect ratio (QPC channel width/length) and gradually disappears as their aspect ratio increases. The physical mechanisms responsible for a decrease in size of the hysteresis loops for QPCs with increasing aspect ratio are: (1) multimode transport in QPCs with larger channel width leading to spin-flip scattering events due to both remote impurities in the doping layer of the heterostructure and surface roughness and impurity (dangling bond) scattering on the sidewalls of the narrow portion of the QPC, and (2) an increase in carrier density resulting in a screening of the electron-electron interactions in the QPC channel. Both effects lead to a progressive disappearance of the net spin polarization in the QPC channel and an accompanying reduction in the size of the hysteresis loops as the lithographic width of the QPC channel increases.
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10
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Kohda M, Okayasu T, Nitta J. Spin-momentum locked spin manipulation in a two-dimensional Rashba system. Sci Rep 2019; 9:1909. [PMID: 30760759 PMCID: PMC6374388 DOI: 10.1038/s41598-018-37967-9] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2018] [Accepted: 12/17/2018] [Indexed: 11/22/2022] Open
Abstract
Spin-momentum locking, which constrains spin orientation perpendicular to electron momentum, is attracting considerable interest for exploring various spin functionalities in semiconductors and topological materials. Efficient spin generation and spin detection have been demonstrated using the induced helical spin texture. Nevertheless, spin manipulation by spin-momentum locking remains a missing piece because, once bias voltage is applied to induce the current flow, the spin orientation must be locked by the electron momentum direction, thereby rendering spin phase control difficult. Herein, we demonstrate the spin-momentum locking-induced spin manipulation for ballistic electrons in a strong Rashba two-dimensional system. Electron spin rotates in a circular orbital motion for ballistically moving electrons, although spin orientation is locked towards the spin-orbit field because of the helical spin texture. This fact demonstrates spin manipulation by control of the electron orbital motion and reveals potential effects of the orbital degree of freedom on the spin phase for future spintronic and topological devices and for the processing of quantum information.
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Affiliation(s)
- Makoto Kohda
- Department of Materials Science, Tohoku University, 6-6-02 Aramaki-Aza Aoba, Aoba-ku, Sendai, 980-8579, Japan. .,Center for Spintronics Research Network, Tohoku University, 2-1-1 Katahira, Aoba-ku, Sendai, 980-8577, Japan. .,Center for Science and Innovation in Spintronics (Core Research Cluster), Tohoku University, 2-1-1 Katahira, Aoba-ku, Sendai, 980-8577, Japan.
| | - Takanori Okayasu
- Department of Materials Science, Tohoku University, 6-6-02 Aramaki-Aza Aoba, Aoba-ku, Sendai, 980-8579, Japan
| | - Junsaku Nitta
- Department of Materials Science, Tohoku University, 6-6-02 Aramaki-Aza Aoba, Aoba-ku, Sendai, 980-8579, Japan.,Center for Spintronics Research Network, Tohoku University, 2-1-1 Katahira, Aoba-ku, Sendai, 980-8577, Japan.,Center for Science and Innovation in Spintronics (Core Research Cluster), Tohoku University, 2-1-1 Katahira, Aoba-ku, Sendai, 980-8577, Japan
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11
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Ho SC, Chang HJ, Chang CH, Lo ST, Creeth G, Kumar S, Farrer I, Ritchie D, Griffiths J, Jones G, Pepper M, Chen TM. Imaging the Zigzag Wigner Crystal in Confinement-Tunable Quantum Wires. PHYSICAL REVIEW LETTERS 2018; 121:106801. [PMID: 30240231 DOI: 10.1103/physrevlett.121.106801] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/04/2018] [Revised: 07/03/2018] [Indexed: 06/08/2023]
Abstract
The existence of Wigner crystallization, one of the most significant hallmarks of strong electron correlations, has to date only been definitively observed in two-dimensional systems. In one-dimensional (1D) quantum wires Wigner crystals correspond to regularly spaced electrons; however, weakening the confinement and allowing the electrons to relax in a second dimension is predicted to lead to the formation of a new ground state constituting a zigzag chain with nontrivial spin phases and properties. Here we report the observation of such zigzag Wigner crystals by use of on-chip charge and spin detectors employing electron focusing to image the charge density distribution and probe their spin properties. This experiment demonstrates both the structural and spin phase diagrams of the 1D Wigner crystallization. The existence of zigzag spin chains and phases which can be electrically controlled in semiconductor systems may open avenues for experimental studies of Wigner crystals and their technological applications in spintronics and quantum information.
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Affiliation(s)
- Sheng-Chin Ho
- Department of Physics, National Cheng Kung University, Tainan 701, Taiwan
| | - Heng-Jian Chang
- Department of Physics, National Cheng Kung University, Tainan 701, Taiwan
| | - Chia-Hua Chang
- Department of Physics, National Cheng Kung University, Tainan 701, Taiwan
| | - Shun-Tsung Lo
- Department of Physics, National Cheng Kung University, Tainan 701, Taiwan
| | - Graham Creeth
- Department of Electronic and Electrical Engineering, University College London, London WC1E 7JE, United Kingdom
| | - Sanjeev Kumar
- Department of Electronic and Electrical Engineering, University College London, London WC1E 7JE, United Kingdom
| | - Ian Farrer
- Cavendish Laboratory, J J Thomson Avenue, Cambridge CB3 0HE, United Kingdom
- Department of Electronic and Electrical Engineering, University of Sheffield, Mappin Street, Sheffield S1 3JD, United Kingdom
| | - David Ritchie
- Cavendish Laboratory, J J Thomson Avenue, Cambridge CB3 0HE, United Kingdom
| | - Jonathan Griffiths
- Cavendish Laboratory, J J Thomson Avenue, Cambridge CB3 0HE, United Kingdom
| | - Geraint Jones
- Cavendish Laboratory, J J Thomson Avenue, Cambridge CB3 0HE, United Kingdom
| | - Michael Pepper
- Department of Electronic and Electrical Engineering, University College London, London WC1E 7JE, United Kingdom
| | - Tse-Ming Chen
- Department of Physics, National Cheng Kung University, Tainan 701, Taiwan
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12
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Yan C, Kumar S, Thomas K, See P, Farrer I, Ritchie D, Griffiths J, Jones G, Pepper M. Coherent Spin Amplification Using a Beam Splitter. PHYSICAL REVIEW LETTERS 2018; 120:137701. [PMID: 29694224 DOI: 10.1103/physrevlett.120.137701] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/18/2017] [Indexed: 06/08/2023]
Abstract
We report spin amplification using a capacitive beam splitter in n-type GaAs where the spin polarization is monitored via a transverse electron focusing measurement. It is shown that partially spin-polarized current injected by the emitter can be precisely controlled, and the spin polarization associated with it can be amplified by the beam splitter, such that a considerably high spin polarization of around 50% can be obtained. Additionally, the spin remains coherent as shown by the observation of quantum interference. Our results illustrate that spin-polarization amplification can be achieved in materials without strong spin-orbit interaction.
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Affiliation(s)
- Chengyu Yan
- London Centre for Nanotechnology, 17-19 Gordon Street, London WC1H 0AH, United Kingdom
- Department of Electronic and Electrical Engineering, University College London, Torrington Place, London WC1E 7JE, United Kingdom
| | - Sanjeev Kumar
- London Centre for Nanotechnology, 17-19 Gordon Street, London WC1H 0AH, United Kingdom
- Department of Electronic and Electrical Engineering, University College London, Torrington Place, London WC1E 7JE, United Kingdom
| | - Kalarikad Thomas
- London Centre for Nanotechnology, 17-19 Gordon Street, London WC1H 0AH, United Kingdom
- Department of Electronic and Electrical Engineering, University College London, Torrington Place, London WC1E 7JE, United Kingdom
| | - Patrick See
- National Physical Laboratory, Hampton Road, Teddington, Middlesex TW11 0LW, United Kingdom
| | - Ian Farrer
- Cavendish Laboratory, J.J. Thomson Avenue, Cambridge CB3 OHE, United Kingdom
| | - David Ritchie
- Cavendish Laboratory, J.J. Thomson Avenue, Cambridge CB3 OHE, United Kingdom
| | - Jonathan Griffiths
- Cavendish Laboratory, J.J. Thomson Avenue, Cambridge CB3 OHE, United Kingdom
| | - Geraint Jones
- Cavendish Laboratory, J.J. Thomson Avenue, Cambridge CB3 OHE, United Kingdom
| | - Michael Pepper
- London Centre for Nanotechnology, 17-19 Gordon Street, London WC1H 0AH, United Kingdom
- Department of Electronic and Electrical Engineering, University College London, Torrington Place, London WC1E 7JE, United Kingdom
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13
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Yan C, Kumar S, Thomas K, See P, Farrer I, Ritchie D, Griffiths J, Jones G, Pepper M. Engineering the spin polarization of one-dimensional electrons. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2018; 30:08LT01. [PMID: 29334361 DOI: 10.1088/1361-648x/aaa7ce] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
We present results of magneto-focusing on the controlled monitoring of spin polarization within a one-dimensional (1D) channel, and its subsequent effect on modulating the spin-orbit interaction (SOI) in a 2D GaAs electron gas. We demonstrate that electrons within a 1D channel can be partially spin polarized as the effective length of the 1D channel is varied in agreement with the theoretical prediction. Such polarized 1D electrons when injected into a 2D region result in a split in the odd-focusing peaks, whereas the even peaks remain unaffected (single peak). On the other hand, the unpolarized electrons do not affect the focusing spectrum and the odd and even peaks remain as single peaks, respectively. The split in odd-focusing peaks is evidence of direct measurement of spin polarization within a 1D channel, where each sub-peak represents the population of a particular spin state. Confirmation of the spin splitting is determined by a selective modulation of the focusing peaks due to the Zeeman energy in the presence of an in-plane magnetic field. We suggest that the SOI in the 2D regime is enhanced by a stream of polarized 1D electrons. The spatial control of spin states of injected 1D electrons and the possibility of tuning the SOI may open up a new regime of spin-engineering with application in future quantum information schemes.
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Affiliation(s)
- C Yan
- London Centre for Nanotechnology, 17-19 Gordon Street, London WC1H 0AH, United Kingdom. Department of Electronic and Electrical Engineering, University College London, Torrington Place, London WC1E 7JE, United Kingdom
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